The present invention relates to an internal combustion engine that takes out rotational motion from an output shaft by converting the reciprocating rectilinear motion of a piston to rotational motion of a crankshaft, and more particularly relates to an internal combustion engine constructed so as to cause reciprocating rectilinear motion of a crankpin through a pinion member and an internal gear member coupled to the crankshaft.
A conventional reciprocating internal combustion engine is known that comprises a combustion chamber formed by a cylinder bore and a piston, a crankshaft including a crankpin off-centered from the axial center of the output shaft, and a connecting rod connected with the crankpin rotatably that oscillates according to the reciprocating rectilinear motion of the piston.
In the aforementioned engine, because the crankpin is formed in an eccentric position off-centered from the axial center of the output shaft by the length of the crank arm, the connecting rod reciprocates vertically while oscillating by a predetermined angle, and the reciprocating rectilinear motion of the piston is converted to rotational motion of the crankshaft, thereby the output shaft rotates.
Due to the structure causing the vertical movement and lateral oscillation of the connecting rod, the coupling part of the connecting rod and piston becomes a rotatively sliding part and the coupling part of the connecting rod and crankpin becomes a rotatively sliding part, and there are provided a plurality of rotatively sliding parts in a 4 cylinder type internal combustion engine. Further, side pressure is also acting on the 4 pistons due to the oscillation of the connecting rod.
The reason of low engine efficiency is generally recognized to be due to theoretical thermal efficiency. However, if the measured data of the source power and the shaft output are compared by performing an integration by multiplying the micro movement distance of the piston by the expansion force, it is easy to recognize that the problem is not limited to theoretical thermal efficiency.
Problems in conventional internal combustion engines include the problem of low thermal efficiency due to exhaust loss as well as the problem of significant loss due to friction and vibration, but many engineers believe that greater improvements is difficult.
As long as there is no change in the angular velocity of a rotating body, an external energy supply is not necessary, however, the general internal combustion engine for automobiles requires a large amount of energy. In other words, a great deal of fuel is consumed when racing including idling. The following shows the fuel consumption measured in P-mode with the air conditioner off with a 1700 ml displacement engine.    Fuel consumption corresponding to 10.4 kW at 1000 rpm    Fuel consumption corresponding to 17.6 kW at 2000 rpm    Fuel consumption corresponding to 26.4 kW at 3000 rpm    Fuel consumption corresponding to 35.2 kW at 4000 rpm    Fuel consumption corresponding to 47.2 kW at 5000 rpm
Data of number of revolution and instantaneous fuel consumption have been compiled for an automobile during normal driving.
More specifically, for instance, when at 2000 rpm the instantaneous fuel consumption in running corresponds to 17.6 kW, the engine is considered to be an idle state without any output. In same manner when the fuel consumption at the same revolution number (rpm) is 30 kW, the difference of 12.4 kW mostly contributes to driving energy. In this case, only 12.4 kW (about 41%) of the 30 kW contributes to driving. However, actual axial output is lowered even more due to its thermal efficiency.
The results of 3 months of collecting this type of data show that 45% of fuel consumption is consumed in maintaining the revolutions of the engine while the remaining 55% is consumed for driving. For example, if the theoretical efficiency is 30%, then only 16% of the fuel consumption contributes to driving. Moreover, when transmission efficiency is added, the amount of contribution for driving becomes an even lower value.
Friction and vibration can be picked up as the cause for generating such conditions. Friction originating in the side pressure between the piston and the cylinder, friction between the piston pin and the connecting rod, friction between the connecting rod and the crankpin, and friction between the crankshaft and the housing can be picked up as such friction. Friction loss is viewed as inevitably increasing due to the inability to secure a sufficient oil film on the reciprocatively sliding parts and rotatively sliding parts.
As for vibration, although there is nothing to do for the vibration due to torque fluctuation in the expansion stroke, vibration in the rotating system cannot be ignored which ultimately becomes heat and is lost. Another problems except the rotating system is energy vibration. In a 4 cylinder engine, all the pistons and connecting rods repeat acceleration and deceleration simultaneously. Although kinetic energy of piston and connecting rod in the upper dead point and lower dead point is zero, at other times it has kinetic energy that is proportional to the square of the speed. Further, in a typical 4-cylinder engine, the four pistons lose speed simultaneously as well as accelerate simultaneously.
The acceleration described above repeats twice for every one rotation, and kinetic energy is given and received in continuous travel between the crankshaft and piston through the link mechanism including the connecting rod. Therefore, while generating vibrations which impact the angular velocity of the crankshaft, friction is generated at the same time in the four link mechanisms with the exchanged kinetic energy in each travel resulting in a large amount of energy loss.
The horizontally opposed 2-cylinder engine in patent document 1 (see FIG. 8) comprises a crankshaft that includes a main shaft for rotary output, a common connecting rod integrally coupled with a pair of horizontally opposing pistons, and a pair of planetary mechanisms equipped between the common connecting rod and the pair of crankpins, and each planetary mechanism comprises a sun gear (stationary internal gear) co-axial with the crankshaft and planetary gears having an outer diameter equal to ½ of the sun gear, and the planetary gears supported rotatably on the crankpin of the crankshaft, and a gear pin is integrally formed on the pair of planetary gears, and coupled to the common connecting rod.
When a piston in the engine described above moves in reciprocating rectilinear motion, there is no oscillating action in the connecting rod and no side pressure on the piston because the gear pin coupled to the common connecting rod moves on the horizontal plane including the rotation axial center of the crankshaft in an reciprocating rectilinear motion according to the roll of the planetary gears.    Patent Document 1: Japanese Patent Publication No.: 2683218
The horizontally opposed 2-cylinder engine of patent document 1 does not have a structure that supports both ends of the common gear pin with bearings but rather supports with a pair of planetary gears and has a structure that supports each of these planetary gears with the crankpins of the crankshaft. Therefore, when a large load applied from the piston acts on the gear pin, the crankpin experiences elastic deformation rendering the gear meshing defective between the planetary gears and the sun gear increasing friction, destabilizing operational reliability, and sacrificing the durability of the planetary gears. Furthermore, supporting the gear pin described above with bearings becomes difficult because the gear pin moves with reciprocating rectilinear motion in the parallel direction with the axial center of the piston.